Segment Information - Results of Operations and Selected Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net interest income	$ 80,190	$ 75,852	$ 239,759	$ 227,133
Noninterest income	39,786	34,575	124,339	101,802
Income before taxes	48,279	25,604	163,364	79,160
Total assets	11,302,771		11,302,771		$ 9,212,357
Operating Segments [Member] | Metropolitan Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	18,728	20,476	57,909	64,970
Noninterest income	5,681	4,735	14,494	14,006
Income before taxes	15,072	6,669	46,598	20,695
Total assets	3,292,422		3,292,422		2,729,886
Operating Segments [Member] | Community Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	47,817	43,369	135,611	131,784
Noninterest income	16,978	15,149	48,151	44,843
Income before taxes	31,722	18,257	98,005	58,225
Total assets	6,558,085		6,558,085		5,527,611
Operating Segments [Member] | Pegasus Bank [Member]
Segment Reporting Information [Line Items]
Net interest income	6,141	5,078	17,308	15,662
Noninterest income	359	379	1,098	631
Income before taxes	2,158	1,429	5,750	4,372
Total assets	1,101,900		1,101,900		919,572
Operating Segments [Member] | Other Financial Services [Member]
Segment Reporting Information [Line Items]
Net interest income	8,718	6,816	30,057	14,304
Noninterest income	12,198	10,882	34,686	31,100
Income before taxes	5,069	3,819	16,240	17,364
Total assets	120,743		120,743		137,122
Operating Segments [Member] | Executive, Operations & Support [Member]
Segment Reporting Information [Line Items]
Net interest income	(1,386)	(104)	(1,784)	196
Noninterest income	45,214	25,969	156,970	79,226
Income before taxes	34,298	17,158	126,428	44,793
Total assets	1,570,064		1,570,064		1,073,507
Eliminations [Member]
Segment Reporting Information [Line Items]
Net interest income	172	217	658	217
Noninterest income	(40,644)	(22,539)	(131,060)	(68,004)
Income before taxes	(40,040)	$ (21,728)	(129,657)	$ (66,289)
Total assets	$ (1,340,443)		$ (1,340,443)		$ (1,175,341)